ABC News is using live election results data from the Associated Press (AP).
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These are the places that will decide who wins control of the Senate.
The midterms are general elections held around the midpoint of a president's four-year term . Hence the name "midterms".
The midterms give voters the chance to decide which political party controls the US House of Representatives and the Senate.
But not all of Congress is up for election.
All 435 seats in the House will be on the ballot, as members of that chamber serve two-year terms. But senators serve six-year staggered terms, meaning just one-third of Senate seats are up for grabs.
The Associated Press (AP) has a dedicated Decision Team of election analysts, researchers and race callers, but they do not make projections or name apparent or likely winners.
"AP only calls a race when we are fully confident that race has been won — defined most simply as the moment the trailing candidates no longer have a path to victory," the agency says.
You can read more about how AP declares winners on their website .
Donald Trump may not be on the ballot, but the outcome of the midterms determines how much power he has to enact his policies for the remainder of his term.
If Republicans lose their majority in either chamber, Mr Trump would need to negotiate with his opponents to get laws passed .
According to the ABC's chief election analyst Casey Briggs, Donald Trump is heading into the midterms with a record low approval rating .
A week out from polling day, the Economist recorded a net approval rating of -27, with 34 per cent of voters approving of the job he's doing and 61 per cent disapproving.
That is a lower net approval rating than any other president has recorded just before their midterm elections since World War II.
Regardless of political stripes, the president's party nearly always goes backwards in the House of Representatives at the midterm elections.
As the ABC's chief election analyst Casey Briggs explains, the Republican Party only needs to lose three seats to lose control of the House , so it's not hard to see why forecasters are tipping a Democrat win.
Early results will start emerging shortly after polls close.
What time that occurs differs by state, but the first polling places to close will be around the east coast and Midwest. For us in Australia, that works out to be 10am AEDT.
Once the midterm results are in, the outcome will immediately begin to shape the remainder of Donald Trump's presidency.
Attention will soon turn to the next presidential election, which is set for November 7, 2028.
You can expect candidates to begin positioning themselves for potential runs, as Mr Trump considers how to cement his legacy in American politics and beyond.
